A decision on whether to vaccinate children as young as five could come in the next 10 days, the head of the UK's vaccine advisory group has said.
Professor Wei Shen Lim, who chairs the Joint Committee on Vaccination and Immunisation (JCVI), said he expected an assessment to be made before Christmas.
But he told MPs that the JCVI was still waiting to hear from the UK's medical regulators on whether they approve the Covid vaccine for younger children.
It comes amid mounting fears over the spread of the Omicron variant, which experts have warned could be running at 200,000 infections per day.
Asked when an assessment would be made on vaccinating over-5s, Prof Shen Lim said: “We are discussing that at the moment. We are also waiting for the vaccines to be approved by MHRA."
Pressed on whether a decision would come before Christmas, he said: "I would expect so. We try and keep in step with the approval process.”
Asked when the MHRA would decide, he said: “I don’t think I should be trying to double guess when they might do that.”
Asked if it was a live decision, he said: “Indeed, yes.”
On Sunday, Education Secretary Nadhim Zahawi said there was "no plan at the moment" to extend the jabs rollout to younger children - but didn't rule it out.
There have been reports of cases of the new Omicron variant in schools, including one in Kent.
The European Medicines Agency (EMA) approved the use of the Pfizer vaccine for children aged 12-15 in May and for children aged five to 11 in November.
The US has also approved the use of Covid jabs in children as young as five-years-old.
Meanwhile the JCVI chief warned Brits may need more regular boosters in future thanks to the decision to rush through a shorter rollout.
He told the Commons Science and Technology Committee that waiting three months, not six, for a booster dose “might mean a lower peak protection”.
He added the shorter gap was only approved on the basis that an “Omicron wave will come soon”.
He told MPs: “If you get the booster at six months and you teach a higher level, say 200, and that wanes at a certain constant rate, to drop from 200 to 50 would take a period of time.
"If you get the booster at three months and the peak level it can get to is lower, say 150, and it wanes at the same rate, it will reach 50 at an earlier time point.”
Asked if that means people may need to get more regular boosters, he replied: “Indeed.
“And that’s why, generally if possible, we try and push out the duration between two doses.”
Prof Wei Shen Lim defended the decision to only ramp up the booster programme on November 29.
He said extending to all over-18s after three months “could” have been announced earlier.
But he told MPs: “I don’t think it would have been appropriate to come earlier.”
He said the Omicron variant was only identified on November 23, and he could not produce “prophetic advice”.
And he said the ideal situation would have been to wait longer than three months before the second and booster dose.
He added: “If the booster were given at three months, it will wane earlier, and a shorter time to boost might mean a lower peak protection.
“So it’s not necessarily true that giving a booster sooner is better.
“If anything, all things being equal, giving a booster as far apart as possible gives the best immune response.
“And so one wants to choose the furthest time point, if one can.”
